12 things to know about Pluto

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Photos:New Horizons explores Pluto, Ultima Thule

The best look at Ultima Thule yet reveals that it has more of a pancake shape.

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Photos:New Horizons explores Pluto, Ultima Thule

New Horizons images revealed that craters on Pluto and Charon were made by small Kuiper Belt objects.

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Photos:New Horizons explores Pluto, Ultima Thule

Although this might look more impressive if you put on 3D glasses, this is the first 3D image of Kuiper Belt object Ultima Thule. New Horizons flew by Ultima Thule on January 1.

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Photos:New Horizons explores Pluto, Ultima Thule

This is the first color image of Ultima Thule, taken at a distance of 85,000 miles from the object by the New Horizons spacecraft. The "red snowman" replaces the initial "bowling pin" shape it was thought to be. This image reveals that Ultima Thule is actually two objects joined by gravity, making it the first contact binary visited by a spacecraft. The red color is due to it being irradiated in the Kuiper Belt.

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Photos:New Horizons explores Pluto, Ultima Thule

New Horizons gave us our first "up-close" look at Ultima Thule on January 1. On the left is a composite of two images taken from half a million miles out, indicating the object's size and shape. An artist's impression at right suggests that Ultima Thule is shaped like a bowling pin and spins like a propeller.

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Photos:New Horizons explores Pluto, Ultima Thule

When NASA's New Horizons spacecraft flew past Pluto in July 2015, it captured this image of the major mountain ranges where it meets a vast icy plain called Sputnik Planitia. The ridges in these photos have now been identified as dunes made of solid methane ice grains.

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Photos:New Horizons explores Pluto, Ultima Thule

New Horizons photographed what scientists are calling "bladed" terrain near the heart-shaped region of the dwarf planet. This 3-D image was created using two images taken about 14 minutes apart on July 14. The first image was snapped about 16,000 miles (25,000 kilometers) from Pluto and the second was taken when the spacecraft was 10,000 miles (about 17,000 kilometers) away. Break out your 3-D glasses for the best view.

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Photos:New Horizons explores Pluto, Ultima Thule

The New Horizons team has discovered a chain of exotic mountains that are covered in methane snow on Pluto. NASA released an image of the snow-capped mountains stretching across the dark expanse of Cthulhu on March 3.

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Photos:New Horizons explores Pluto, Ultima Thule

NASA released a photo on February 4, 2015, of what it suspects is an image of floating hills on Pluto's surface. The hills are made of water ice and are suspended above a sea of nitrogen.

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Photos:New Horizons explores Pluto, Ultima Thule

This image made in infrared light shows water ice is abundant on Pluto's surface. The image was created using two scans of Pluto made by the New Horizons spacecraft on July 14, when the probe was about 67,000 miles (108,000 kilometers) above Pluto.

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Photos:New Horizons explores Pluto, Ultima Thule

This image shows the layered interior walls of the planet's many craters. According to NASA, "layers in geology usually mean an important change in composition or event." However, NASA says the New Horizons team members do not know if they are seeing local, regional or global layering.Most of the craters seen here lie within the 155-mile (250-kilometer)-wide Burney Basin. Learn more at NASA's website.

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Photos:New Horizons explores Pluto, Ultima Thule

This image shows how erosion and faulting has sculpted Pluto's icy crust into rugged badlands. The prominent 1.2-mile-high cliff at the top is part of a great canyon system that stretches for hundreds of miles across Pluto's northern hemisphere, NASA says. Learn more at NASA.gov.

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Photos:New Horizons explores Pluto, Ultima Thule

Pluto's largest moon, Charon, in seen in enhanced color in this image taken by NASA's New Horizons spacecraft. The space probe took the image just before it made its closest approach on July 14. The image combines blue, red and infrared images to best highlight the moon's surface features. Charon is 754 miles (1,214 kilometers) across. The image was released on October 1.

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Photos:New Horizons explores Pluto, Ultima Thule

Images from two instruments on New Horizons are combined in this photo to show Charon's cratered uplands at the top and a series of canyons. The bottom of the image shows rolling plains.

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Photos:New Horizons explores Pluto, Ultima Thule

This composite of enhanced color images shows the striking differences between Pluto, lower right, and its largest moon, Charon. NASA says the color and brightness of the two worlds have been processed identically to allow for direct comparison. Pluto and Charon are shown with approximately correct relative sizes, but their true separation is not to scale.

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Photos:New Horizons explores Pluto, Ultima Thule

These photos show Pluto's variety of textures, including what NASA calls "rounded and bizarrely textured mountains." The mountains are informally called the Tartarus Dorsa. This image shows about 330 miles (530 kilometers) of Pluto's terrain. It combines blue, red and infrared images taken by the space probe's Ralph/Multispectral Visual Imaging Camera. The images were taken on July 14, during the probe's flyby. They were released on September 24.

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Photos:New Horizons explores Pluto, Ultima Thule

The photos taken by New Horizons just before its closest approach to Pluto on July 14 are the sharpest images to date of Pluto's varied terrain. This high-resolution image reveals details of two ice mountains. The image spans 75 miles (120 kilometers) of Pluto's surface.

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Photos:New Horizons explores Pluto, Ultima Thule

This image of the surface of Pluto was taken just 15 minutes after NASA's New Horizon spacecraft made its closest approach to the icy planet on July 14. As it looked toward the Sun, the spacecraft's camera captured more than dozen thin layers of haze in Pluto's atmosphere, at least 60 miles (100 kilometers) above the surface. The photo was downlinked to Earth on September 13.

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Photos:New Horizons explores Pluto, Ultima Thule

This image of Pluto's icy and mountainous landscapes was taken from a distance of 11,000 miles (17,700 kilometers). "This image really makes you feel you are there, at Pluto, surveying the landscape for yourself," said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Colorado.

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Photos:New Horizons explores Pluto, Ultima Thule

This picture is a synthesis of new high-resolution images downlinked from New Horizons. The broad icy plains have been nicknamed Sputnik Planum. This image is from a perspective above Pluto's equatorial area. Astronomers began downlinking a data dump from the space craft over Labor Day weekend, September 5 to 7.

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Photos:New Horizons explores Pluto, Ultima Thule

Scientists say that what looks like mountains could be huge blocks of frozen water suspended in frozen nitrogen. On the new photos, taken on July 14 and released on September 10, a pixel is 400 meters (440 yards). New Horizons' closest pass by Pluto took it about 50,000 miles from the surface.

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Photos:New Horizons explores Pluto, Ultima Thule

Pluto's landscape has lots of variety: plains, mountains, craters and what looks like they might be dunes. The smallest details on the photos are about half a mile wide. The area with the craters is ancient, scientist say. The smooth frozen planes are relatively young.

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Photos:New Horizons explores Pluto, Ultima Thule

Just before its closest approach to Pluto on July 14, NASA's New Horizons spacecraft snapped this photo of Charon, Pluto's largest moon. The photo was shot at a distance of 290,000 miles away. Charon's north pole region is markedly dark. This photo was released on September 10.

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Photos:New Horizons explores Pluto, Ultima Thule

This new image of Pluto is stunning planetary scientists. It shows the small world's atmosphere, backlit by the sun. NASA says the image reveals layers of haze that are several times higher than predicted. The photo was taken by the New Horizons spacecraft seven hours after its closest approach to Pluto on July 14. New Horizons was about 1.25 million miles from Pluto at the time.

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Photos:New Horizons explores Pluto, Ultima Thule

Images taken of Pluto's heart-shaped feature, informally named Tombaugh Regio, reveal a "vast, craterless plain that appears to be no more than 100 million years old," NASA said July 17. The frozen region "is possibly still being shaped by geologic processes." NASA's New Horizons spacecraft was launched in 2006 and traveled 3 billion miles to the dwarf planet.

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Photos:New Horizons explores Pluto, Ultima Thule

Close-up images of a region near Pluto's equator revealed a giant surprise: a range of youthful mountains. NASA released the image on July 15.

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Photos:New Horizons explores Pluto, Ultima Thule

Remarkable new details of Pluto's largest moon, Charon, are revealed in this image released on July 15.

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Photos:New Horizons explores Pluto, Ultima Thule

The latest spectra analysis from New Horizons' Ralph instrument was released on July 15. It reveals an abundance of methane ice, but with striking differences from place to place across the frozen surface of Pluto.

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Photos:New Horizons explores Pluto, Ultima Thule

NASA team members and guests count down to the spacecraft's approach to Pluto on July 14.

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Photos:New Horizons explores Pluto, Ultima Thule

This image of Pluto was captured by New Horizons on July 13, about 16 hours before the moment of closest approach. The spacecraft was 476,000 miles from Pluto's surface.

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Photos:New Horizons explores Pluto, Ultima Thule

The colors in this image of Pluto and Charon are exaggerated to make it easy to see their different features. (These are not the actual colors of Pluto and Charon, and the two bodies aren't really that close together in space.) This image was created on July 13, one day before New Horizons was to make its closest approach to Pluto.

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Photos:New Horizons explores Pluto, Ultima Thule

This image of Pluto was captured by New Horizons on July 12. The spacecraft was 1.6 million miles from Pluto at the time.

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Photos:New Horizons explores Pluto, Ultima Thule

New Horizons snapped this photo of Charon on July 12. It reveals a system of chasms larger than the Grand Canyon. The spacecraft was 1.6 million miles away when the image was taken.

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Photos:New Horizons explores Pluto, Ultima Thule

New Horizons was about 3.7 million miles from Pluto and Charon when it took this image on July 8.

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Photos:New Horizons explores Pluto, Ultima Thule

Do you see a heart on Pluto? This image was taken on July 7 by New Horizons when it was about 5 million miles from the planet. Look to the lower right, and you'll see a large bright area -- about 1,200 miles across -- that resembles a heart.

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Photos:New Horizons explores Pluto, Ultima Thule

New Horizons took six black-and-white photos of Pluto and Charon between June 23 and 29. The images were combined with color data from another instrument on the space probe to create the images above. The spacecraft was 15 million miles away when it started the sequence and 11 million miles when the last photo was taken.

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Photos:New Horizons explores Pluto, Ultima Thule

Pluto is shown here along with Charon in images taken on June 25 and 27. The image on the right shows a series of evenly spaced dark spots near Pluto's equator. Scientists hope to solve the puzzle as New Horizons gets closer to Pluto.